Power plant



C. F. HAWLEY Oct. 9, 1962 POWER PLANT 2 Sheets-Sheet 1 Filed June 27, 1960 JNVENTOR. Charles FTFlaurZey Mm Oct. 9, 1962 Filed June 27, 1960 c. F. HAWLEY 3,057,165

POWER PLANT 2 Sheets-Sheet 2 PRIMARY SUPERHEATER FINAL SUPERHEATER NORMAL CYCLE 225 MW DRUM y'pouwos or STEAM STEAM GENERATOR REHEATER yPouwos or WATER 3' POUNDS F STEA 1.93 y PIP/NI. fl-INTERM. FINAL POUNDS SUPERHEATEE SUPERHEATER OF STEAM y POUNDS .93 3; POUNDS or STEAM or STEAM DRUM m I 0 I! .75} Pouuos u or STEAM Z .2 (l! u E 5 U u I F 2 w w n u flsypouuns" OF STEAM 3+ .933 pouuos I or WATER IN VEN TOR.

Charles F ILzwley United States Patent ()filice 3,057,155 Patented Got 9, 1962 3,657,165 PGWER PLANT Charles F. Hawley, Hoiden, Mass, assignor to Riley toher Corporation, Worcester, Mass, a corporation of Massachusetts Fiied June 27, 195i), Ser. No. 38,905 2 Claims. (Ci. 60-73) This invention relates to a power plant and more particularly apparatus arranged to produce mechanical power for generation of electricity by burning various fuels.

One of the most important problems encountered in the generation of steam in large central stations is that there are occasions when the demand for electricity is much greater than normal. These are called peak periods. In some central stations which have a large number of boilers, it is usual practice to supply the normal electric load by using the steam generating units and the turbines which have the greatest efiiciency; one boiler and turbine, usually an antiquated set, is used to pick up the peak load. The difiiculty with this system of practice is that, first of all, the unit which is used as the peaking unit, even through it is old and was purchased at a time of low cost, nevertheless represents a portion of the overhead or capitalization of the entire plant, and it is poor practice from the point of view of economy to use a portion of a plants capital assets only occasionally. Another method of handling this problem is to design the steam generating unit and the turbine-generator set, of such a large capacity that they will handle the peak load. The difiiculty here is that during the normal load (which may be a very high percentage of the time) only a portion of the capacity is being used. This means that one has spent a great deal of money for a large unit but uses it only partially, which is poor practice from a business point of view. Furthermore, it should be noted that the portion of the unit which supplies the peaking load does not necessarily have to be too efficient, although, of course, it is important that the portion of the plant which supplies the normal load should be at the optimum efliciency. Neither of the two methods of supplying peak load described above is adequate, although certainly the second method is preferable to the first because of the fact that it represents a so-called spinning reserve which is always capable of picking up the extra load immediately, whereas in the former method it is necessary to start up the peaking unit and this takes a considerable amount of time. Another method of taking care of the peaking problem, which has been used from time to time, is to provide an auxiliary prime mover which will be started up immediately; such prime loaders are usually diesel engines, gas turbines, and so on, rather than the conventional steam turbine. This has the advantage, of course, of being immediately available, but has the disadvantage that a considerable capital investment is not being used most of the time. Many of the problems thus presented by the prior art have been obviated in a novel manner by the present invention.

It is, therefore, an outstanding object of the invention to provide a power plant capable of supplying substantial peaking load capacity which has a substantial spinning reserve and is immediately capable of picking up a load above normal.

Another object of this invention is the provision of a power plant for converting fuel energy to mechanical energy in which there is very little idle capacity and all capital assets are being continually used.

A further object of the present invention is the provision of a power plant having a steam generating unit and a steam turbine in which the cost of added capacity to take care of peaking load is very low.

It is another object of the instant invention to provide a power plant having a steam generating unit and a steam turbine capable of peaking operation wherein the efliciency during peaking operation does not drop as low as in previously-known peaking units.

Although the novel features which are believed to be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself, as to its objects and advantages, the mode of its operation, and the manner of its organization may be better understood by referring to the following description taken in connection with the accompanying drawings forming a part therof, in which:

FIG. 1 is a vertical sectional view of a steam generating unit to be used in the power plant of the invention;

FIG. 2 is a schematic view of a power plan cycle of the prior art; and

FIG. 3 is a power plant cycle according to the present invention.

Referring first to FIG. 1, wherein are best shown the general features of the invention, the power plant, indicated generally by the reference numeral 10, is shown as consisting of a steam generating unit 11 supported in a structural framework 12. and a steam turbine 13 mounted on a foundation 14. The steam turbine 13 consists of a high-pressure section 15 and a low-pressure section 16 connected to an electrical generator (not shown). The steam generating unit 11 comprises in general of a boiler 17 and a furnace 18. The boiler 17 consists of a steam-and-water drum 19 into which feed water is introduced and which is connected by downcomer tubes 21, 22, 23 and 24 to headers 25 and 26. These headers serve water wall tubes 27 which line the walls of the furnace 18 and define a combustion chamber 28. Other downcomer tubes 29 lead to a lower end of a water platen 31 extending into the combustion chamber 28. The upper end of the combustion chamber 28 is connected to an upper pass 32 whose rearward end is connected to the upper end of a back pass 33 divided by a wall into a forward portion 34 and a rearward portion 35 having dampers 36 at their lower ends. These passes are connected to a dust collector 37 and to a rotary regenerative air heater 38. The gas exit of the air heater is, of course, connected to a stack (not shown). At the side of the combustion chamber opposite the water platens 31 are located low temperature radiant superheater platens 39 which receive steam from the steamand-water drum 19. The steam-and-water drum is connected to a steam header 41 from which back pass wall tubes 42 lead the steam to a collector header 43 which, in turn, is connected by a pipe 44 to the low end of the superheater platens 39. The upper end of the platens 39 are connected to an intermediate superheater 45 lying in the upper pass 32. This superheater is in turn connected to another high temperature superheater 46. The outlet end of the high-temperature superheater 36 is connected by a pipe 47 to the inlet end of the high-pressure section 15 of the steam turbine. The outlet end of the high-pressure section 15 of the steam turbine is connected by a pipe 48 to the inlet end of a reheater 49 located in the rearward portion 35 of the back pass 33. The outlet end of the reheater 49 is connected to a high-temperature reheater 51 which is connected by means of a pipe 52 to the inlet end of the low-pressure section 16 of the steam turbine. The intermediate superheater 45 is provided with an outlet drum 53 which is connected to the inlet end of the high-temperature superheater 46. At the same time, it is connected by a pipe 54 to the inlet side of a pressure regulating valve 55, the outlet end of which is connected to the pipe 48 leading to the reheater 49.

At the bottom part of the rearward portion 35 of the back-pass 33 is located an economizer 56 which receives feed water from a pipe 57. The outlet of the economizer 56 is connected to another economizer 58 located in the forward section 34 of the back pass. The outlet of the economizer 58 is connected by a pipe 59 to the steamand-water drum 19. The furnace 13 is of the type shown and described in the patent of Craig No. 2,85 3,059 and in general is restricted in its intermediate portion to define a lower high-temperature combustion chamber 61 which is arranged for tapping of molten slag. Suitable burners 62 are located in the undersides of the noses which define the restriction and provide for suitable combustion in the chamber 61.

The steam turbine 13 is of an unusual type. The highpressure section 15 is designed to handle a flow of steam which would be encountered at a normal load, while the low pressure section 16 is designed to handle not only the normal load but also an additional amount suflicient to produce mechanical power and, eventually generate electrical power equal to the amount made necessary by a peaking load; in other words, the capacity of the lowpressure section 16 is such to handle a steam flow sufficient to provide the energy existing between normal load and peaking load.

The operation of the invention will now be readily understood in view of the above description. Feed water reaches the power plant through the pipe 57, passes through the economizer 56 and the economizer 58, through the pipe 59 to the steam-and-water drum 19. Water leaves the steam-and-water drum and passes downwardly through the downco-mer tubes 21, 22, 23, 24 and 29, thus providing water for upward flow through the water wall tubes 27 and through the water platens 31. During this upward movement the water is converted into steam which passes into the steam-and-Water drum 19 for collection and treatment in the usual manner. The steam passes from the steam-and-water drum into the superheater header 41 and then downwardly through the tubes 42 which line the back pass 33 into the collecting header 43 from which they pass downwardly through the pipe 44 to the lower end of the superheater platens 39. The steam flows upwardly through the platens 39 into the convection intermediate superheater 45 from which it passes into the high-temperature superheater 46 and thence through the pipe 47 to the inlet end of the highpressure section 15 of the steam turbine. After passing through the high-pressure section the steam passes through the pipe 48 to the inlet end of the reheater 49 from which it passes upwardly into the pipe 2, leading to the lowpressure section 16 of the steam turbine. The products of combustion, resulting from the introduction of fuel and air through the burner 62 into the high-temperature combustion chamber 61, pass upwardly through the combustion chamber 28 in radiant heat transfer relationship to the water platens 31 and the low-temperature superheater platens 39. The gases pass over the high-tempera ture superheater 45, and the high-temperature superheater 46 in the upper pass 32. Then, they pass rearwardly and downwardly through the back pass 33 over the surfaces of the economizer 58 in the forward portion 34 and over the reheater 49 and the economizer 56 in the rearward portion 35 of the back pass. The division of gases between the forward portion 34 and the rearward portion 3-5 is determined by the settings of the dampers 36. The gases pass then through the dust collector 37 and the air heater 38 to the stack (not shown).

Now, during normal operation, the amount of heat released in the steam generating unit 11 is determined by the amount of air and fuel flowing through the burners 62. Sufficient water is provided by the feed water pumps to the pipe 57 into the boiler to supply adequate steam to the steam turbine to support the load demanded. The necessary load, of course is determined in the power plant by suitable electrical instruments indicating the electrical demand of the system which the power plant is supposed A to support. When the load increases to a peaking condition, the amount of water introduced into the system through the pipe 57 increases by an amount determined by such a peak. The water flowing through the economizer into the steam-and-water drum and then through the water walls and water platens exceeds the normal amount by the amount of this peak. However, when the superheated steam is passed through the platens 39' and through the intermediate superheater 45, the excess of steam over and above the normal amount is diverted through the pipe 54 and the valve 55 directly to the pipe 38 leading to the reheater 49. The amount of steam which is allowed to pass from the superheater header 53 into the final high-temperature superheater 46 is only the normal amount. Since this normal amount goes to the high pressure section 15 of the steam turbine, it is. only this normal amount which is returned through the pipe 48 to the reheater 49. This is true, that is to say, until the excess peaking amount is added through the valve 55 to the pipe 48 so that the amount of steam passing through the reheater 49 is equal to the normal amount plus an excess of steam determined by the peaking condition. This peaking amount of steam eventually is introduced into the low-pressure section 16 of the turbine so that the low-pressure section of the turbine operates at a much higher load than normally, whereas the high-pressure section operates at the high efiiciency of normal load.

An illustration of the cycle of the invention can be made by observing FIGS. 2 and 3 and comparing the appli-oan-ts cycle to that of a conventional method of peaking operation. FIG. 2 shows a normal reheat cycle to produce 225 megawatts of electricity under normal efficient operating conditions. This is the standard operating cycle in which about 90% of the steam goes back to the reheater and is heated to 1000 F. and then goes to the low-pressure section of the turbine. The 10% of steam which is apparently lost is accounted for by feed water heating and various other auxiliary services. If this conventional system is operated at Y plus 90% Y lbs. of water for a 90% peaking load, the efiiciency of the turbine will drop to as low as 78 or 80%.

In FIG. 3, it is conceived that the peaking load which is 315 megawatts will bring about a somewhat reduced turbine generator and boiler efiiciency. This scheme involves the use of approximately the same high-pressure end of the turbine, but with a low-pressure end which will pass a much larger amount of steam than normal to pick up the increased megawatts. The diagram shows that the normal amount of steam is used, which is designated as Y plus .93Y lbs, which mixes with the reheated steam passing to the reheater. All of the steam is generated and goes through the primary superheater at which point part of it is by-passed directly to the reheater mixing with the reheat return from the low-pressure sections of the turbine which in this case is only about 75% of the steam which enters the high-pressure section. The total is then heated to the 1000 degree F. level and returned to the low-pressure end of the turbine. It is conceived that the efiiciency of the system prepared by the applicant would be only about 1 /2% less than the efficiency for which the unit was designed at normal operating load.

There are two operating advantages which appear with this type of arrangement. The first benefit lies in the fact that the unit constitutes a spinning reserve which is always capable of a peaking operation as fast as the fuel and combustion can be increased. This is quite dififerent from the so-called peaking unit as conventionally conceived in that it is immediately ready to take the load and does not require time to start up and place an extra unit on the line. This is considered by many utilities of being extremely important. The second point is that the efficiency of the peaking load with the present apparatus falls 01? only a small amount, whereas the efficiency for so-called conventional peaking unit might drop as low as 78 or 80%. i

While certain novel features of the invention have been shown and described and are pointed out in the annexed claims, it will be understood that various omissions, substitutions and changes in the forms and details of the device illustrated and in its operation may be made by those skilled in the art without departing from the spirit of the invention.

The invention having been thus described, what is claimed as new and desired to secure by Letters Patent is:

1. A power plant capable of peaking operation on occasion, comprising a steam generating unit having a superheater and a reheater, the superheater consisting of a radiant section, an intermediate section, and a hightemperature section in series, a steam turbine including a high-pressure section and a low-pressure section, the lowpressure section having substantially greater capacity than the high-pressure section by an amount determined by the peaking operation, a by-pass pipe extending from the outlet of the intermediate section of the superheater to the entrance to the reheater, and regulating means including a pressure-reducing valve located in the said by-pass pipe to permit an amount of dry steam from the intermediate section to pass through the pipe equal in amount to the excess steam capacity of the low-pressure turbine.

2. A power plant capable of peaking operation on occasion, comprising a steam generating unit having a superheater and a reheater, the superheater consisting of a low-temperature section and a high-temperature section in series, a steam turbine including a high-pressure section and a low-pressure section, the low-pressure section having substantially greater capacity than the highpressure section by an amount determined by the peaking operation, a by-pass pipe extending from the outlet of the low-temperature section of the superheater to the entrance to the reheater, and regulating means including a pressure-reducing valve located in the said by-pass pipe to permit an amount of dry steam from the lowtemperature section of the superheater to pass through the pipe equal in amount to the excess steam capacity of the low-pressure turbine.

References Cited in the file of this patent UNITED STATES PATENTS 2,602,433 Kuppenheimer July 8, 1952 2,649,079 Van Brunt Aug. 18, 1953 2,685,280 Blaskowski Aug. 3, 1954 2,852,005 Buri Sept. 16, 1958 FOREIGN PATENTS 1,064,869 France Dec. 30, 1953 821,790 Germany Nov. 19, 1951 OTHER REFERENCES Germany printed application 1,043,347 (KL 14th 1/14), Nov. 13, 1958. 

